This article examines changes in the valency marking in the history of English. I start with a discussion of the typological literature on measuring basic valency and point out the problems with such an approach. A sample of 18 Old English verbs provides no basic valency pattern for Old English; this makes Old English different from the other Germanic languages. I then review the evidence, presented in, for instance, Visser (1963), that there is an increase in transitivity in the history of English and argue that this increase is partly due to verbs ceasing to mark Theme-preserving alternations, between anticausative and causative. I also examine Theme-changing alternations, between intransitive and transitive, and argue that, due to the changes in aspect marking, objects become licensed by a light verb, v. I conclude by suggesting a syntactic structure that accounts for the various stages of English and argue that the main changes are due to an increase in morphological intransparency.